Unix Shells by Example truly fulfills
the claim made in the title: over 630 examples are in the book,
plus another 60 in the first appendix. If you want to learn shell
programming, this book is a must-have.

The first chapter introduces the three major shells: the
Bourne shell, the C shell and the Korn shell. The Bourne Again
shell (bash), the one used by most Linux users, isn't specifically
covered, but the information on the other three shells usually
applies. A history of each shell, plus the theory behind shells is
given. Where the shell comes in on a UNIX system is described, as
well as more general UNIX topics such as file attributes and
permissions.

Chapter Two, “The UNIX Tool Box”, gives a very useful
explanation of regular expressions which applies to much more than
shell programming; for example, searching for text within Emacs or
vim is built on basically the same principle. Over the next six
chapters, what are considered to be three of the more important
UNIX tools in regard to shell programming are covered.

Our friend grep appears in
the third chapter—the meaning behind the name, how it works, and
how to use it (with, of course, extensive examples). Chapter Four
covers sed, the Streamlined
Editor—again, replete with examples.

The next three chapters describe
awk--the history, the input
format, records and fields, patterns and actions, script files,
comparison expressions, variables, pipes, loops and arrays, to name
just a few topics. This section is quite extensive and very useful.
I would have to agree with the author that these three are among
the most important of all text processing utilities.

Each of the three major shells is covered in a separate
chapter. Chapter Eight introduces the Bourne shell, discussing
topics such as variables, metacharacters, file-name substitution,
pipes, functions, arithmetic, looping and the built-in shell
commands, in addition to many other subjects of interest.

The C shell appears in the next chapter. Each shell is given
basically the same treatment: the first section of the chapter is
devoted to the interactive shell (aliases, job control, the
environment, redirection, etc.), while the second section covers
programming in that shell (loops, flow control, arithmetic, etc.).
Chapter Ten goes over the Korn shell in the same manner.

Appendix A lists useful utilities for shell programmers.
These are stock UNIX programs, such as at, mv, passwd and so on.
Quite a few examples are given (sixty, to be precise), as well as
usage information and a short description. Appendix B provides a
table for comparing the three shells. This is an invaluable
resource for those who need to port shell scripts from one shell to
another. For example, the table shows you how, in each shell, to
assign the output of a command to a variable. In the C shell you
use set d='date', in the Bourne shell you use
d='date', and in the Korn shell you use
d=$(date) or d='date'.
Appendix C explains clearly and concisely how to use quoting
correctly, especially for those tricky problems where you have
multiple layers of quotes. The attached CD comes with all source
code given in the book.

So, is the book worth your time and money? Yes, very much so.
I found the examples to be particularly helpful, illustrating
concepts far more clearly than prose could possibly do. If you're
interested in shell programming, or even if you're just curious
about shells in general, get over to your local bookstore and buy
this book.

Ben Crowder
is a young Linux aficionado living in
Utah. In addition to fiddling with the insides of computers, Ben
enjoys reading, writing and music. He can be reached at
mlcrowd@enol.com.